A ruthlessly efficient 36-8 win by Manly over the Sydney Roosters has come at a cost with co-captain Jason King, winger William Hopoate and centre Steve Matai all suffering injuries.

King, the cornerstone of the Sea Eagles' bruising pack, was forced to leave the Brookvale Oval field after 20 minutes and early reports suggested he could miss the rest of the season with a pectoral injury.

Hopoate left the field after scoring two tries to have his hamstring iced while Matai, who also bagged a try double, went down with an apparent neck problem in the match's dying minutes.

Manly consolidated second place on the ladder with the eight tries-to-two victory in front of 13,745 fans in stormy conditions, while the hapless Roosters are yet to win away this year and remain in a fight to avoid the wooden spoon.

Des Hasler's troops (34 points, +169) are two points up on the Broncos and four ahead of the Cowboys in fourth, but they are still two wins back from the Storm (38, +233) with four rounds to play.

Daly Cherry-Evans said the team had put last weekend's loss to the Tigers behind it and was looking forward to moving on as September football looms.

"Last week was a little bit of a bump, but we're more than happy to come to Brookie Oval and set that aside and get some momentum going into this finals series," he told Grandstand.

"These are the sort of wins that you look back on and build off - that second half was outstanding, so big credit to the boys."

The next month will prove tough for Manly, with home stands against Canterbury and Melbourne bookended by games on the road at Parramatta (round 23) and Brisbane (round 26).

Cherry-Evans said that while the injuries his side suffered were a blow, there could be a silver lining considering the Sea Eagles' difficult run to the semis.

"We were lucky that the score was as massive as it was because we got to rotate the boys on the bench and got to give the hard-working back rowers a hard-earned rest," he said.

"I think they'll appreciate that.

"Parramatta's always tough, this time it's on their territory. We were lucky to get the win last time we played them [at home in round 15] so hopefully we can get the points."

Manly forward Glenn Stewart was more measured in his assessment of the weeks to come, saying that while the victory will build confidence, the Sea Eagles also must remain calm.

"There's still another month to go before we start getting to that [finals]," he said.

"But I'm sure Dessy will keep our feet firmly on the ground and it's very cliche but it'll be week to week until we get there.

"The Tigers, everyone was saying that they were a little bit shaky before last week's game but they came out and rolled us so every week's a challenge."

As well as Hopoate and Matai, Jamie Lyon, Cherry-Evans, Stewart and Tony Williams scored tries for the Sea Eagles, while Lyon had an off day with the boot with two from eight.

For the Roosters Aidan Guerra and Phil Graham scored four-pointers but Todd Carney missed on both conversion attempts.

The Sea Eagles led 12-0 after three first-half tries and extended that by four just five minutes after the break when Glenn Stewart picked up the ball from the back of a scrum 10m out and dummied his way to the line.

It was 22-0 four minutes later when wrecking ball Williams ran over Mitchell Pearce and Lyon finally nailed a conversion.

It started getting embarrassing for the Roosters when Kieran Foran was ruled to have performed a one-on-one strip on Jason Ryles and the five-eighth sent centre Matai over.

The Roosters got one back through Guerra in the 63rd before Hopoate's second four minutes later from a superb Brett Stewart offload.

Matai's second, when he slammed the ball down despite being held by several Roosters defenders, made it 36-4 before the Roosters scored the try of the match, Graham completing an amazing length-of-the-field effort in the final minute.